Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The tower of a wind turbine is typically constructed from a plurality of tower cans or segments. Each tower segment generally comprises a steel plate that has been rolled and welded at the ends to form a circular shape. The circular shaped tower segments may then be stacked one on top of the other to form a hollow tower structure. Additionally, to provide access to the interior of the hollow tower structure, a doorway is typically formed in one or more of the tower segments.
Conventional wind turbine doorways are typically formed by cutting an oval-shaped aperture out of one or more of the tower segments and welding a corresponding oval-shaped doorway frame within the aperture. The doorway frame typically comprises a heavy, steel plate that has been rolled to match the curvature of the tower segments. Unfortunately, such a conventional doorway has several drawbacks. For example, to ensure that the doorway frame is properly installed within the tower, the aperture must be precisely cut out from the tower segment using a complex cutting process that is very time consuming and expensive. Additionally, the oval-shaped aperture generally defines an area of high stress concentration within the tower segments, thereby requiring the thickness of the tower segments to be increased in order to accommodate the additional stress. Moreover, the heavy, rolled doorway frames are typically difficult to manufacture and must be custom-made to match the particular curvature of the tower segments in which the doorway frame is being installed. Such curved doorway frames also require a correspondingly curved door, thereby further increasing the manufacturing time and expense necessary to form the tower doorway.
Accordingly, there is a need for a tower doorway that addresses many of the issues indentified in the prior art.